The present invention pertains to an apparatus for driving a long narrow probe into the ground to assist in the location of leaks in natural gas pipelines. The probes have a number of different names including needle bar, pin, searcher bar, and plunger bar. The bar which is typically a ½ inch-⅝ inch steel rod is driven into the ground using a slide hammer to a depth of about 3 feet or more. The needle or probe is then pulled out of the ground and the gas concentration in the hole is measured with a hand-held detector. By driving a number of holes and measuring the difference in gas concentration in each, utility personnel can determine the size and position of the leak more accurately and, therefore, minimize size and extent of an excavation needed to find and repair the leak.
Slide hammer operation may be undertaken by utility workers and others many times during the day and the activity is known to cause repetitive stress injury. More recently, it has been determined that removing or pulling the probe from the ground is more damaging than the probe driving operation. Removing the tool by typical current methods requires lifting the 10-15 lb. hammer against the force of gravity and, in addition, the impact of the weight against the probe on retraction tends to compress the spine of the worker, significantly increasing the likelihood of injury.
Probe pulling devices are known in the industry to eliminate the purely manual lift-to-remove technique. These devices are similar to a conventional fence post puller in which a long lever is pivoted on an axis close to a gripping jaw around the post that may be operated by hand or by foot. Utility workers do not favor these pullers because they are awkward and heavy and are difficult to carry along with the probe driver and gas analyzer.
Recently activity has been devoted to the development of a combined needle or probe driver and remover but, to date, no such device has found any significant industry acceptance.